Then Mayweather laughed and everyone in the room relaxed and laughed along with him.

PODCAST: Leonard Ellerbe and Dan Wetzel talk Mayweather-McGregor

It’s easy to laugh and make jokes when you’re days away from earning yet another nine-figure check, as Mayweather will do when he puts his 49-0 record and reputation as the greatest boxer of his generation on the line in a 12-round match against UFC lightweight champion Conor McGregor on Aug. 26 at the T-Mobile Arena in Las Vegas.

It’s almost a license to print money. The cheapest seat at the top of the 21,000-seat T-Mobile Arena went for $500. Close to the ring, seats were $10,000.

The pay-per-view cost is $100 in the U.S. A closed-circuit seat in Las Vegas is $150. To watch it in a movie theater will set you back $40.

Floyd Mayweather and Conor McGregor made waves with their uncomfortable (and at times inappropriate) media tour. (Getty)

If McGregor wins, or if the fight is reasonably competitive, it would seem at least one rematch might occur given the money involved.

But there is no rematch clause. If McGregor defeats Mayweather, he is under no legal or contractual obligation to face Mayweather again. If Mayweather pulls out a disputed decision, McGregor has no way to legally force Mayweather’s hand to do it again.

UFC president Dana White said at the kickoff news conference for the event that he wanted no part of a rematch.

“To even talk about a rematch or even think about a rematch, we have to see what the fight is like first,” White said. “Listen, if Floyd Mayweather versus Conor McGregor is one of the greatest fights you’ve seen in your life, you know it would probably be something you’d have to consider. Otherwise … I want to go back to my world after this.”

Though the UFC will, as all participants will, make a lot of money, it’s thrown White’s company into chaos. He’s been promoting a boxing match for the last two months, and was negotiating a boxing match for the three months prior to that.

McGregor, his biggest star, has never defended either of the titles he’s won and he will have had exactly one MMA fight in 371 days prior to his match with Mayweather.

The UFC needs McGregor to get back into the cage, defend his title and get back on its regular rhythm. If McGregor chooses to retire after the fight, a bout for the vacant championship can be put together and the division will move on.

Mayweather is a heavy favorite and never seriously thought of taking the fight, until he realized how much money he could make from it. Given that McGregor has no boxing experience, it made sense to him to try to make the match.

But if there were talk of a rematch, it likely couldn’t be put together quickly enough to happen again before the end of the year. That means it would have to occur in 2018, when Mayweather turns 41.

The only way there would even be a thought of a rematch would be if McGregor were to win; if Mayweather were to win a disputed decision; or, in the most unlikely scenario, it was a Fight of the Year-type match that the public demanded to see once again.

The chances, though, are tiny. If Mayweather gets anywhere near the $300 million he says he’ll earn, that means he’ll be at close to $600 million in his last three fights. At 40 and climbing, he doesn’t need to put himself through it.

McGregor won’t need to fight again, either, though he’s insisted he’ll return to fight in the UFC by December.

But unless something that very few believe will happen occurs, Mayweather-McGregor looks almost certain to be a one-and-done event.